The Incas were ambitious farmers, and to maximise agricultural production, they transformed the landscape with terracing, canals, and irrigation networks, whilst wetlands were often drained to make them suitable for farming. In addition, the Incas were fully aware of the values of regular crop rotation, and they also fertilized the land with dried llama dung, guano, or fish heads if these materials were available. Even so, the often harsh Andean climate could bring floods, droughts, and storms which, along with disease, meant that annual crop failures were not infrequent. In such cases the Inca talent for food storage came into its own.